REM sleep,naps, and depression

Continued interest in rapid eye movement (REM) sleep abnormalities in depression stimulated comparative studies on daytime naps versus nighttime sleep. In a group of 15 depressed patients, REM latencies in morning and afternoon naps were similar to the shortened REM onset at night. Although REM latency did not vary across the three times, the propensity for REM sleep appeared to be greater in the morning nap than in the afternoon nap and the early portion of nocturnal sleep. Finally, the data suggest that responders to tricyclic treatment tend to be poor sleepers during daytime naps.     

EEG sleep in young depressives: first and second night effects

The sleep electroencephalogram (EEG) of young, drug-free, recurrently depressed outpatients was analyzed for 2 nights and was compared to age-matched controls using a variety of standard and computerized measures of sleep activity. On the first night, young depressives showed significantly greater difficulty in falling asleep and decreased sleep efficiency. Sleep architecture differences between the young depressives and controls were highlighted by increased percentages of Stage 2 sleep and major decreases in Stages 3 and 4 (delta wave) sleep among the depressives, as indicated by either period analyses or spectral analysis. The greatest differences in delta wave activity during night 1 were found in the first two (non-rapid eye movement (NREM) periods as measured by period analysis (NREM period 1, p less than 0.04; NREM period 2, p less than 0.001--average delta wave count) or by spectral analysis for the first 100 min of sleep (0.5-2.0 Hz). In contrast to the NREM sleep findings, various REM variables, including REM latency did not significantly distinguish the two subject groups for either night 1 or 2. Stepwise discriminant analysis demonstrated that night 1 sleep latency and delta wave counts during the second NREM period correctly classified 100% of all 16 individuals studied. The only differences between the young depressed patients and controls that remained on night 2 were significant reductions in slow-wave sleep as quantified by the computerized methods. Taken together, these findings suggest that the EEG response of young outpatients to the first night's stay in a sleep laboratory may be a useful tool for the diagnosis of depression in this age group. In addition, the use of computerized methods in this study point to an underlying deficit in delta sleep waveforms as being a prominent feature of the sleep of young depressed subjects.     

Sleep and affective disorders. A minireview

The most predictable electroencephalographic sleep changes of major depression are a shortened first NREM sleep period, a prolonged first REM period (with increased density of rapid eye movements), sleep continuity disturbance, and diminished slow wave sleep (with shifting of delta activity from the first to the second NREM sleep period). The more rapid appearance of the first REM sleep period occurs in relation to sleep onset but not apparently in relation to clock time. The changes occurring in the first NREM-REM cycle of the night appear to be relatively specific to major (particularly endogenous) depression. Depressed men appear to have diminished nocturnal penile tumescence compared with healthy controls, but depressed patients generally do not have a higher incidence of sleep apnea or nocturnal myoclonus. The sleep physiologic changes of depression appear to persist into clinical remission, suggesting that they are trait-like. Published studies appear to support the conclusion that there is a close link between the regulation of sleep and the regulation of mood in affective illness.     

Changes in EEG power density during sleep laboratory adaptation in depressed inpatients.

BACKGROUND: The aim of the present study was to evaluate the first-night effect in depressed inpatients, using standard sleep measures as well as all-night spectral analysis of the sleep electroencephalogram (EEG). METHODS: Eighteen drug-free, depressed inpatients were studied for 3 consecutive nights in the hospital sleep laboratory. RESULTS: Visual sleep scoring results showed a slight but measurable first-night effect, characterized by a reduction of rapid eye movement (REM) sleep amount and increased wakefulness. Sleep EEG spectral analysis showed significantly reduced delta (p <.01) and theta (p <.05) power density in non-REM (NREM) sleep of the first night compared with that of the second and third nights. These differences were limited to the early part of the sleep period, a time during the night that is particularly vulnerable to the effects of depressive disorder. In contrast to the NREM sleep findings, spectral REM variables studied did not significantly vary across the three nights. CONCLUSIONS: The results obtained suggest that first-night data should not be simply discarded but could be used in subsequent analyses and could be considered useful in the evaluation of the sleep of depressed patients.     

Sleep and treatment response in depression: new findings using power spectral analysis

This study examined quantitative measures of sleep electroencephalogram (EEG) and phasic rapid eye movements (REM) as correlates of remission and recovery in depressed patients. To address correlates of remission, pre-treatment EEG sleep studies were examined in 130 women outpatients with major depressive disorder treated with interpersonal psychotherapy (IPT). To address correlates of recovery, baseline and post-treatment EEG sleep studies were examined in 23 women who recovered with IPT alone and 23 women who recovered with IPT+fluoxetine. Outcomes included EEG power spectra during non-rapid eye movement (NREM) sleep and REM sleep and quantitative REMs. IPT non-remitters had increased phasic REM compared with remitters, but no significant differences in EEG power spectra. IPT+fluoxetine recoverers, but not IPT recoverers, showed increases in phasic REM and REM percentage from baseline to recovery. In NREM sleep, the IPT+fluoxetine group showed a decrease in alpha power from baseline to recovery, while the IPT group showed a slight increase. The number of REMs was a more robust correlate of remission and recovery than modeled quantitative EEG spectra during NREM or REM sleep. Quantitative REMs may provide a more direct measure of brainstem function and dysfunction during REM sleep than quantitative sleep EEG measures.     

Influence of cedar essence on spontaneous activity and sleep of rats and human daytime nap

Abstract We investigated whether exposure to the odor of extracted cedar essence (CE) has (i) an influence on spontaneous activity and Sleep-wake states of rats and (ii) a sleep-promoting effect on human daytime nap after taking an ordinary night's sleep. In rats exposed to CE, spontaneous activities and amount of wake were significantly decreased, while the amount of non-rapid eye movement (NREM) sleep was significantly increased. In human daytime nap, NREM sleep stage 2 latency was significantly shortened after exposure to CE.     

INFLUENCE OF AGE ON THE INTERRELATION BETWEEN EEG FREQUENCY BANDS DURING NREM AND REM SLEEP

The age-dependence of temporal interrelations between distinct frequency bands of sleep EEG was investigated in a group of 59 healthy young and middle-aged males via cross correlation analysis. Based on global evaluation throughout the entire night, a highly significant decline of the delta/theta correlation with increasing age was found. A separate analysis for non-rapid eye movement (NREM) and rapid eye movement (REM) sleep revealed different changes with aging. During NREM sleep, the correlation between the delta and theta frequency bands decreased with increasing age. In contrast, during REM sleep, a stronger correlation became obvious between the theta, alpha, and beta frequency bands with increasing age, whereas the lower frequency components were not affected. These findings indicate that aging processes seem to interact with sleep EEG rhythms in a complex manner, where most conspicuous is a disintegration of the activities in the lower frequency range, both concerning the successive sleep cycles across the night and the microstructure of NREM sleep     

Influence of age on the interrelation between EEG frequency bands during NREM and REM sleep

The age-dependence of temporal interrelations between distinct frequency bands of sleep EEG was investigated in a group of 59 healthy young and middle-aged males via cross correlation analysis. Based on global evaluation throughout the entire night, a highly significant decline of the delta/theta correlation with increasing age was found. A separate analysis for non-rapid eye movement (NREM) and rapid eye movement (REM) sleep revealed different changes with aging. During NREM sleep, the correlation between the delta and theta frequency bands decreased with increasing age. In contrast, during REM sleep, a stronger correlation became obvious between the theta, alpha, and beta frequency bands with increasing age, whereas the lower frequency components were not affected. These findings indicate that aging processes seem to interact with sleep EEG rhythms in a complex manner, where most conspicuous is a disintegration of the activities in the lower frequency range, both concerning the successive sleep cycles across the night and the micro-structure of NREM sleep.     

Daytime sleep patterns of primary depressives: A morning nap study

The electroencephalographic sleep patterns of 10 primary depressives were recorded during baseline nights and two morning nap sessions using a fixed time schedule. Averaged sleep measures for baseline nights replicated previous findings of altered rapid eye movement (REM) sleep patterns and sleep continuity. REM sleep during morning naps occurred only in patients with elevated REM indexes on baseline and prenap nights; it failed to appear in morning sleep of patients who exhibited contrasting REM characteristics. An analysis of hourly REM sleep distribution and averaged deviations from group means revealed significant differences between the two groups which could account for the uneven daytime REM propensity.     

The sleep EEG's microstructure in depression: alterations of the phase relations between EEG rhythms during REM and NREM sleep

OBJECTIVE: We investigated the microstructure of sleep electroencephalograms (EEGs) of 13 unmedicated depressive inpatients and 13 healthy controls matched in sex and age, hypothesizing that depressives depict an alteration of certain EEG oscillations across the night. METHODS: We digitized the sleep EEGs with a sampling rate of 100 Hz (bipolar derivation C(z)-P(z), 1440 single sweeps; 2048 data points each), calculated the time course of delta (1-3.5 Hz), theta (3.5-7.5 Hz), alpha (7.5-15 Hz), and beta (15-35 Hz) activity over the night, and determined the correlation coefficients of these different EEG rhythms separately for rapid eye movement (REM) and non-rapid eye movement (NREM) sleep. RESULTS: For both groups we detected a clear difference between REM and NREM sleep cycles at certain frequency bands. The most impressive changes occurred for the delta/beta and theta/beta correlations, which change their signs between NREM (negatively correlated) and REM (positively correlated) sleep cycles. Following an analysis of variance model with repeated measurement design, a statistically significant group effect (P=0.024) between depressives and controls was observable during NREM sleep for the delta/beta (P=0.010) and theta/beta (P=0.018) interactions. CONCLUSION: We detected alterations of certain sleep EEG oscillations during the NREM sleep cycle, where the delta/beta as well as the theta/beta activities were higher (negatively) compared to healthy controls. Together with previous investigations on the influence of antidepressants on the microstructure of sleep EEGs, this is another hint that the NREM sleep cycle plays a major role in depression.     

Sleep deprivation as a probe in the elderly

Decreased slow-wave sleep (SWS) and sleep continuity are major effects of healthy aging and of associated psychopathological states. Using sleep deprivation, we studied the extent to which age- and psychopathology-related sleep "decay" is reversible in aged normal, depressed, and demented subjects. Depression or probable Alzheimer's dementia compromised the augmentation of sleep continuity and SWS seen in healthy elderly following sleep deprivation. Rapid eye movement (REM) latency decreased during recovery sleep in the controls but increased in both patient groups. Compared with demented patients, depressed elderly had greater severity of sleep continuity disturbance both before and after sleep deprivation, a more protracted course of recovery sleep, and increased slow-wave density in the second non-REM (NREM) sleep period (during recovery). The REM sleep time was diminished in dementia compared with depression both at baseline and during recovery sleep. These differential effects of age, health, and neuropsychiatric disease on recovery from sleep loss are relevant to recovery or reversal theories of sleep and have implications for daytime well-being in the elderly.     

Sleep stage II contributes to the consolidation of declarative memories

Various studies suggest that non-rapid eye movement (NREM) sleep, especially slow-wave sleep (SWS), is vital to the consolidation of declarative memories. However, sleep stage 2 (S2), which is the other NREM sleep stage besides SWS, has gained only little attention. The current study investigated whether S2 during an afternoon nap contributes to the consolidation of declarative memories. Participants learned associations between faces and cities prior to a brief nap. A cued recall test was administered before and following the nap. Spindle, delta and slow oscillation activity was recorded during S2 in the nap following learning and in a control nap. Increases in spindle activity, delta activity, and slow oscillation activity in S2 in the nap following learning compared to the control nap were associated with enhanced retention of face-city associations. Furthermore, spindles tended to occur more frequently during up-states than down-states within slow oscillations during S2 following learning versus S2 of the control nap. These findings suggest that spindles, delta waves, and slow oscillations might promote memory consolidation not only during SWS, as shown earlier, but also during S2.     

Rem sleep in depressed patients: Different attempts to achieve adaptation

Twenty-seven depressed patients and 10 healthy subjects were investigated in the sleep laboratory during two to three consecutive nights. Eleven of the 27 patients demonstrated the “first night effect” (group I) and 11 other patients demonstrated a clear absence of the “first night effect” (group II). Five of the 27 depressed patients were omitted from the study because they did not fit criteria for first night effect. The 10 healthy controls demonstrated a first night effect. In group I, the duration of the first rapid eye movement (REM) sleep episode was increased on the first night and on the second night the REM sleep latency was decreased, whereas REM sleep duration and eye movement (EM) density was increased. The number of the short sleep cycles (less than 40 minutes) was greater in group I versus group II and the percentage of slow-wave sleep (SWS) was also higher in group I. In depressed patients with the “first night effect” the enhanced REM sleep requirement is satisfied not only by an increased REM sleep duration but also by the improved REM sleep quality that is crucial for adaptation. The adaptive role of the increased first REM period and the increased EM density in this period is very limited.     

Rapid eye movement sleep characteristics during and after mood-disturbing events

Twenty-nine women undergoing divorce were monitored for six nights to explore the relation of mood disturbance and rapid eye movement (REM) sleep. Follow-up evaluations were completed on 13 women one to two years later. The more traditional women were more depressed and had shortened REM latencies. Depression was also related to an irregular eye movement density sequence throughout the night. Although depression and REM latency were both significantly improved at follow-up, the REM latency of those initially most depressed remained at a lower than normal level and the eye movement density sequency remained irregular, suggesting some lag in the sleep response or a traitlike vulnerability to future depression.     

Spectral characteristics of sleep EEG in chronic insomnia

To determine whether the spectral characteristics of the sleep electroencephalogram (EEG) of insomniacs differ from that of healthy subjects, we compared in each of the first four non-rapid eye movement (NREM) and rapid eye movement (REM) episodes: (a) the time courses of absolute power, averaged over the subjects in each group, for the delta, theta, alpha, sigma and beta frequency bands; (b) the relationship between these time courses; and (c) the overnight trend of integrated power in each frequency band. The results show that NREM power, for all frequencies below the beta range, has slower rise rates and reaches lower levels in the insomniac group, whereas beta power is significantly increased. In REM, insomniacs show lower levels in the delta and theta bands, whereas power in the faster frequency bands is significantly increased. Thus, the pathophysiology of insomnia is characterized not only by the generally acknowledged slow wave deficiency, but also by an excessive hyperarousal of the central nervous system throughout the night, affecting both REM and NREM sleep. This hyperarousal is interpreted in terms of the neuronal group theory of sleep which provides a possible explanation for the discrepancies observed between subjective impressions and objective measures of sleep. Also, it is suggested that the progressive hyperpolarization of the thalamocortical neurons as sleep deepens is slower in the patient population and that this may explain the observed slow wave deficiency. The homeostatic control of slow wave activity, on the other hand, would appear to be intact in the patient population.     

The immediate effects of nasal continuous positive airway pressure treatment on sleep pattern in patients with obstructive sleep apnea syndrome

We studied the immediate effects of continuous positive airway pressure (CPAP) applied nasally on the pattern of sleep in 12 patients, aged 30-58 years, with obstructive sleep apnea syndrome. All patients demonstrated a moderate to severe syndrome on the control night; apnea index ranged 28-83 apneas/h sleep. Nasal CPAP completely abolished all obstructive apneas and allowed apnea-free breathing in all 12 patients. Nasal CPAP had a marked effect on the sleep pattern. It significantly reduced stage I/II non-rapid eye movement (NREM) sleep and markedly increased stage III/IV NREM and REM sleep on the first treatment night. Stage I/II NREM sleep decreased from a control of 62.7 +/- 2.3% to 29.1 +/- 2.3% on the first treatment night. Stage III/IV NREM sleep increased from a control of 6.7 +/- 1.6% to 31.5 +/- 1.6%. The rebound in this sleep stage was especially marked in 3 patients aged 55-58 years. REM sleep increased from a control of 18.4 +/- 2.0% to 30.6 +/- 2.0% on the first treatment night. There was an increase in REM density. All patients were treated for another 2 nights and their sleep pattern analyzed on the third night. All sleep stages were still significantly different to the control night. The possible mechanisms involved are discussed.     

Overnight polygraphic study of Lennox-Gastaut syndrome

Nine children with Lennox-Gastaut syndrome, aged 2-14 years, were studied by overnight polygraphy for one night. Percentage of sleep period time (SPT) for stage rapid eye movement (REM) and REM density during REM sleep decreased in Lennox-Gastaut syndrome as compared with control. Alpha rhythm was seen in only 3 cases and sleep spindles in only 6 cases. The effect of sleep-wake or REM-non-REM (NREM) sleep rhythm on the rate of generalized epileptiform discharges varied with the individual. Ictal discharges with or without clinical tonic seizures observed in 5 children appeared during NREM sleep and awakening in the morning, and in 2 of these cases they also occurred frequently during the NREM sleep of the first sleep cycle. Subclinical ictal discharges were also seen during REM sleep in the early morning in one case who was 2 years old. The Lennox-Gastaut syndrome is assumed to involved a considerable degree of brain stem dysfunction.     

Sleep modulation of interictal spike configuration in untreated children with partial seizures

Spontaneous changes in interictal spike morphology were evaluated before initiation of antiepileptic drug (AED) therapy in 38 children with uncontrolled partial seizures. Nonrapid eye movement (NREM) sleep during the first third of the night was associated with spikes of higher amplitude, longer duration, and lower degree of sharpness than those observed in wakefulness or REM sleep. Spike amplitude decreased in subsequent NREM epochs, but duration and sharpness remained relatively consistent. A NREM/REM modulatory pattern was identified, with REM periods exhibiting spikes of decreased amplitude, shorter duration, and increased sharpness as compared with NREM periods in each third of the night. The spike changes associated with REM sleep are similar to the alterations previously described as occurring coincidentally with attainment of seizure control and thus may reflect inherent modulation of epileptogenicity in synchrony with sleep cycles.     

Rapid eye movement dependent central apnea with periodic leg movements

Central sleep apnea is a period of at least 10 s without airflow, during which no ventilatory effort is present. Most of the central apneas occur in Non-Rapid eye movement (NREM) sleep. Central apnea occuring in Rapid eye movement (REM) sleep is extremely rare. We present our patient who had a diagnosis of obstructive sleep apnea in another sleep center since 2003. His Auto Continuous Positive Airway Pressure (CPAP) machine was disrupted so he admitted to our center to renew his machine and for daytime sleepiness while using his machine. The polysomnography revealed central apneas ending with respiratory arousals and periodic leg movements in rapid eye movement (REM) stage. We found no cause for central apneas. The patient benefited from servo ventilator therapy. We present this case as an unusual form of central apnea with the review of the literatures. Even the patients diagnosed as obstructive sleep apnea should be analyzed carefully. The diagnosis and the therapeutic approach may change in the favor of the patient.     

Effects of auditory stimulation during rapid eye movement sleep in healthy volunteers and depressed patients.

Auditory and somesthesic forms of stimulation have substantially increased rapid eye movement (REM) sleep in cats. We investigated whether auditory stimulation, applied during REM sleep or outside REM sleep, would have similar effects in normal volunteers. We also administered auditory stimulation to depressed patients during REM sleep. Subjects were studied during 1 acclimatization night, 2 baseline nights, 4 consecutive nights with auditory stimulation, and 1 followup night without auditory stimulation. Normal volunteers were randomly divided into Group R, which received auditory stimulation during each REM sleep episode, and Group NR, which received auditory stimulation at the end of each REM sleep episode. Depressed patients (Group D) received auditory stimulation during each REM sleep period. Only Group R showed increased REM sleep time during the nights of auditory stimulation and throughout the followup night. This group also increased their sleep efficiency. Group NR showed reduced sleep efficiency due to an increase in both the duration and frequency of awakenings. Group D did not show increased REM sleep time, but did show shortened REM sleep episodes, increased REM sleep frequency, and increased duration of awakenings. Group D did not show clinical changes.